Jim's Corner Blog

Messier Objects in Ursa Major: A Mini-Messier Marathon


Ursa Major

RA 12h 20.0m

Dec +58°22′

Mag 9.0 and 9.3


Alternate: NGC 3031, Bode’s Galaxy

Ursa Major

RA 9h 55.6 m

Dec +69º 04′

Magnitude 6.9


Alternate: NGC 3034

Ursa Major

RA 9h 55.8 m

Dec +69º 04′

Magnitude 8.4


Alternate: Owl Nebula

Ursa Major

RA 11h 12.0m

Dec +55º18′

Mag 9.6


Alternate: M102

Ursa Major

RA 14h 3m 2s

Dec +54º35′

Mag 9.6


Ursa Major

RA 11h 08m 7s

Dec +55º57′

Mag 10.0


Ursa Major

RA 11h 55.0m

Dec +53º39′

Mag 11.0

With March fast approaching, now is a good time to practice Messier object location finding and observational skills. Ursa Major is a perfect constellation to familiarize with deep sky observing, with seven Messier objects within this favorite constellation.

As an somewhat odd start, M40 is NOT a deep sky object, but a double star! Historians have long felt that Charles Messier mistook this double star for a nebula. But it must still be accounted for in a mini- or full Messier Marathon. M40 is easily observed with a four-inch telescope.

M81 and M82 are a cosmic duet pair of galaxies is one of the deep sky showpieces that captures the imagination of every backyard astronomer. Easily seen through a 4-inch refractor on a dark moonless night and a favorite target for 8-inch SCT owners, M81 and M82 are separated by only 38′. M81 and M82 can even be seen through 50-mm or greater binoculars from a dark country site.

Pierre Mechain independently recovered both galaxies in August 1779 and reported their positions to his friend Charles Messier. Messier added both galaxies to his catalog after his position measurements on February 9, 1781.

The pronounced grand-design spiral galaxies M81 and M82 are part of a nearby group called M81. M81 is characterized in the Hubble classification system as a classic Sa-type galaxy, while M82 is an irregular or IO classification. Astronomers believe tens of million years ago, a close encounter occurred between the galaxies M81 and M82. During this near-miss, the larger and more massive M81 has dramatically deformed M82 by gravitational interaction. The encounter has also left traces in the spiral pattern of the brighter and larger galaxy M81, first making it overall more pronounced, and second in the form of the dark linear feature in the nuclear region. The galaxies are still close together, their centers separated by a linear distance of only about 150,000 light years.

This pair of galaxies can be seen with 12×60 or 20×80 binoculars, and occasionally with 7×50 binoculars by sharp-eyed observers in very dark sites. My f/7.8 4-inch refractor with a wide-field 24-mm eyepiece with an AFOV of 68ºyields a magnification of 36x and a true field of 2.24º. This combination easily captures M81 as a bright oval haze and M82 as a slim cigar shape. The 8-inch SCT with the same eyepiece at 83x and a true FOV of 0.98º begins to show a hazy halo of nebulosity around M81, with M82 displaying a nucleus. Higher magnifications will help bring out the detail, and a larger telescope will bring out additional detail.

The Owl Nebula, M97, is a planetary nebula that is noted for features that faintly resembles an owl’s head. The Owl Nebula monicker was attached to M97 following Lord Rosse’s observations of the planetary nebula through his famous 72-inch Leviathan of Parsonstown.

This is an object that benefits form the use of a large aperture telescope or the use of an UHC nebula filter or OIII nebula filter. The “owl eyes” are clearly obvious with a telescope of apertures larger than 8”, especially with a nebula filter. Dark skies and nebula filter is needed with smaller apertures.

The Owl Nebula is an interesting object to test the effectiveness of light pollution filters and nebula filters. Under suburban skies, even an eleven inch SCT had difficulty seeing M97 without a filter aid. The addition of an LPR filter enabled sighting the Owl with averted vision. However the use of an OIII or UHC filter enabled the direct observation of the Owl Nebula even under light polluted suburban skies.

M101 was initially discovered by Pierre Mechain in 1781. He later that year made a duplicate observation of this galaxy, which was cataloged by Messier as M102. Mechain retracted is

his M102 sighting in 1783, realizing his duplication mistake. Thus, in counting Messier objects captured during a mini- or full Marathon, this galaxy counts as two objects.

M101 in astrophotos is a beautiful face-on Sc spiral galaxy with clearly separated arms filled with blue stars. The arms can be observed in telescopes of double digit apertures, but the spiral shape will not be seen in a four inch refractor. Instead only the central concentration of stars can be seen.

M108 is a Sc spiral galaxy seen from a nearly edge-on perspective. Another Pierre Mechain discovery from his 1781-1782 observations. This rather large object can be seen in dark skies through binoculars, and is easily captured by a four-inch refractors and 120x or higher. It is only 1ºfrom M97. It is visually a series of mottled patches of light. Larger apertures brings a broken patched structure into view.

M109 is an unspectacular barred galaxy that can be seen through binoculars just 1ºfrom the Ursa Major star Phecda at the bottom of the Big Dipper bowl. Seen through a 4-inch refractor the bright central region can be seen. M109 is another Pierre Mechain discovery during his productive 1781-1782 period.

Locating and observing Ursa Major Messier objects is good practice for the March Messier Marathon, or half-marathon if you want to go to sleep at midnight!